drm/panfrost: Get rid of the unused JS_STATUS_EVENT_ACTIVE definition

Exception types will be defined as an enum.

v4:
* Fix typo in the commit message

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210630062751.2832545-5-boris.brezillon@collabora.com